This application claims priority to Japanese Patent Application No. P2000-377989.
1. Field of the Invention
The present invention relates to a thin film magnetic head used for recording/reproduction in a magnetic disk storage apparatus, a manufacturing method therefor, and a magnetic disk storage apparatus and disk array system in which to mount the thin film magnetic head.
2. Description of the Background
Along with an increase in the recording density of magnetic disk storage apparatuses, the coercive force of the recording media has also been increased. A need has been recognized in the art to provide a material having a high saturation magnetic flux density (Bs) that is capable of producing a magnetic field strong enough to write into a high coercive medium for the magnetic core material or writing heads.
Materials having a high saturation magnetic flux density include CoNiFe (Bs greater than 1.7T) which has a higher Bs than Ni45Fe55 that is currently used as the magnetic core material (Bs: 1.6T) as described in JP-A-89422/1994, JP-A-241503/1996, JP-A-346202/1994 and JP-A-3489/1995. Further, Japanese Patent Publication No. 2821456 discloses a method of preparing a plated layer with a high Bs using a bath without the addition of saccharine sodium in the plating solution composition.
To attaining a magnetic disk storage apparatus with high recording density, it may be necessary to use a layer forming technique capable of stably forming a magnetic core with an increased thickness for generating a more intense magnetic field. The technique includes the use of a material with a high saturation magnetic flux density (Bs) capable of producing a sufficient magnetic field to write into a high coercive force medium.
As described in Japanese Patent Publication No. 2821456, the Coxe2x80x94Nixe2x80x94Fe soft magnetic material layer prepared from a bath that does not contain a stress relieving agent has a Bs of at least 1.9T and a Hch of no more than 2.5 Oe. Because since the stress of the plated layer is large, peeling may ensure in a formed layer with a thickness greater then approximately 2.0 xcexcm, making the layer formation difficult.
Further, as described in JP-A-346202/1994, the soft magnetic Coxe2x80x94Nixe2x80x94Fe material layer prepared from a bath containing a stress relieving agent may provide a layer with a low coercive force of approximately Hch=0.4 Oe. However, assuming the peak intensities at fcc (111) face, fcc (200) face and bcc (110) face in the X-ray diffraction as I(111), I(200) and I(110), respectively, such a layer could not be obtained unless a substantially face-centered cubic system was formed having a peak intensity ratio of 0.1xe2x89xa6I(200)/I(111)xe2x89xa60.2 and annealing was applied after the formation of the layer. Further, unevenness may increase in the surface shape of a layer if the layer composition is deviated in a region containing a slight amount of body-centered cubics in the face-centered cubics, which results in clouding and an inability to obtain a gloss layer.
As can be seen from the conventional applications described above, it is difficult to stably mass produce magnetic heads having high saturation magnetic flux density capable of producing sufficient magnetic fields which correspond to a high recording density.
To address one or more of the above limitations in the conventional devices, in accordance with at least one preferred embodiment of the present invention, a magnetic layer containing Co, Ni and Fe is formed by a sputtering method as a plated underlayer and a magnetic layer containing Co, Ni and Fe is formed on the plated underlayer by an electroplating method to form a magnetic pole layer. In accordance with this invention, Co, Ni and Fe are preferably present as: 40 wt %xe2x89xa6Coxe2x89xa670 wt %; 10 wt %xe2x89xa6Nixe2x89xa625 wt %; and 10 wt %xe2x89xa6Fexe2x89xa630 wt % in the sputtered layer as the plated layer and the plated underlayer. Further, in accordance with this invention, only bcc is preferably observed for the sputter layer as the plated underlayer under X-ray diffraction, and the peak intensity ratio is: I(200)/I(111)xe2x89xa70.5 and I(110)/I(111)xe2x89xa71, when defining peak intensities in fcc (111) face, fcc (200) face, and bcc (110) face in the X-ray diffractiometry for the plated layer as I(111), I(200) and I(110), respectively.
A small peak intensity ratio I(200)/I(111), I(110)/I(111) means that crystals are intensely oriented to the face-centered cubic fcc (111) face. The films which are substantially fcc described in JP-A-34020/1994, Japanese Patent Publication No. 2821456 belong to this case. However, since the present invention preferably uses a soft magnetic thin film in which the constitutional ratio of the face-centered cubic system and body-centered cubic system (ratio for the body-centered cubic system and the face-centered cubic system in the magnetic layer) is: 40%xe2x89xa6body-centered cubic systemxe2x89xa680% and 20%xe2x89xa6face-centered cubic systemxe2x89xa660%, and face-centered cubic system+body-centered cubic system is 100%, it may suffice that the peak intensity ratio is I(200)/I(111)xe2x89xa70.5 and I(110)/I(111)xe2x89xa71. In addition, since a lot of body-centered cubic system is contained in the layer, the deviation in the layer composition, if any, preferably has no effect on the surface shape of the layer, and a glossy layer can be prepared stably as in this invention.
Additionally, by using a CoNiFe layer also for the plated underlayer, the crystallinity of the plated layer is enhanced, and the crystallographic orientation can be controlled more easily with the present invention compared to the conventional applications. When the CoNiFe layer is used partially or entirely for the upper magnetic pole of the writing head, since the underlayer is situated on the side of the magnetic gap relative to the lower magnetic pole, the saturation magnetic flux of the underlayer, when using a permalloy layer for instance, is lower than that of the plated layer which decreases the writing magnetic field.
On the contrary, when the CoNiFe layer is used according to this invention, it preferably has a saturation magnetic flux density equal to or greater than the plated layer to improve the characteristics of the head. When different kinds of metals are laminated, they may lead to cell reactions that may possibly corrode the CoNiFe plated layer, but such corrosion may be avoided when the CoNiFe layer is used also for the underlayer, as in at least one preferred embodiment of the present invention.
The CoNiFe magnetic thin film of the present invention may form a CoNiFe magnetic plated layer containing saccharine sodium by preparing the layer from a plating bath containing saccharine sodium as a stress relieving agent and conducting the electroplating under the following preferred conditions: a bath temperature within the range from 25xc2x0 C. to 35xc2x0 C.; a current density from 3 to 12 mA/cm2; and a pH value from approximately 3.2 to 4.0. A thick layer of at least 3 xcexcm may also be formed by conducting plating under the plating conditions described above.
Further, the magnetic characteristics of the soft magnetic layer obtained according to preferred embodiments of the present invention may have: a saturation magnetic flux density Bs of: 17500 gaussxe2x89xa6Bs less than 20000 gauss; a coercive force in the difficult axis direction Hch of: Hch less than 1.50 Oe; and a saturation magnetic flux density of the underlayer that is greater than the Bs of the plated layer. While JP-A-3489/1995 describes that the coercive force is increased at the peak intensity ratio: I(200)/I(111)xe2x89xa70.2, a coercive force of Hch less than 1.5 Oe is preferably attained by the present invention thus avoiding one or more of the conventional difficulties.
Further, in a recording/reproducing separation type thin film magnetic head using a magnetoresistive element for the reading device and an induction type magnetic head for the writing device, recording may be possible to a recording medium with a coercive force of at least 4000 Oe by using the soft magnetic CoNiFe layer partially or entirely as the lower and upper magnetic cores of the writing head according to the present invention.
Additional objects, features and/or advantages of the invention will appear more fully from the following description of the invention, drawings, and attached claims.